1. FIELD OF THE INVENTION
This invention relates to refractory materials and to a process for producing such materials from red mud. More particularly, the invention relates to such refractory materials which are suitable for use as cell linings in aluminum production cells.
2. DESCRIPTION OF THE PRIOR ART
Red mud is a by-product of alumina production processes and it is often discarded as waste, but this is economically and environmentally disadvantageous. Many attempts have been made over the years to find a use for red mud but none has proved to be particularly satisfactory. For example, since red mud contains a large proportion of iron oxide, attempts have been made to smelt the mud for the recovery of iron but without commercial success.
British patent 1,491,432 published on Nov. 9, 1977 in the name of Chemokomplex Vegyipari Gep-Es Berendezes Export-Import Vallalat et al, discloses the use of red mud for the production of shaped ceramic products. This is achieved by mixing the red mud with silica, silicates or similar materials, or dolomite to the extent of 10-49% by weight (on a dry weight basis), shaping the resulting mixture and then firing it at 950.degree.-1250.degree. C. However, the resulting materials are not satisfactory for applications involving alkaline and fluorine corrosion at high temperature, such as cell linings for aluminum production cells where cryolite components, mainly NaF, are involved. Moreover, the products have a tendency to shrink during firing and thus may crack.